Good news, an old newsroom canard goes, doesn't sell newspapers. It's true that it's the rare reader who wants to read about the ship that didn't sink, the house that didn't catch fire, the hurricane that blew itself out to sea.

But sometimes the good news is the most thrilling news of all, and this week there are two items of news nothing short of thrilling about the march of medicine through Africa, where the news is almost never good.

The World Health Organization announced that that an entire year, 365 happy days, had passed without a single case of polio reported anywhere on the African continent. The Global Polio Eradication Initiative, led by the World Health Organization, now thinks eradication of polio, the childhood crippler and killer that once terrified every parent with the advent of summer, can be achieved by the year 2018. The last two places that remain in peril are Pakistan and Afghanistan.

The other good news is that ebola virus disease, which emerged from close by the Ebola River valley in the Congo to slay thousands and terrify millions, is on the run and may soon be dispatched to the place where germs go to die. The number of new cases, measured in the thousands in Sierra Leone, Guinea and Liberia only a few months ago, has dipped below 10 a week, and the most momentous of all, Lancet magazine, the prestigious British medical journal, reports that a new Ebola vaccine has tested "100 percent effective."

Across the globe, medical authorities, who are taught to respect caveats and restrain their enthusiasm in announcements of medical breakthroughs, are little short of giddy (for scientists). "We believe that the world is on the verge of an efficacious Ebola vaccine," says Marie Paule Kieny, the assistant director-general of the World Health Organization. "It could be a game-changer."

The vaccine is a genetically engineered hybrid of the benign "vesicular stomatitis" virus and a strain of the Ebola virus from Zaire. Clinical trials of the vaccine were conducted in Guinea, one of the hardest hit of the African countries. Giddy or not, the scientists celebrating the breakthrough issue the usual caveats: more tests lie ahead, there's a lack of test comparisons with placebos, or harmless imitations of vaccine, and early studies are always subject to statistical flukes.

The usual method of testing a new vaccine is to test it against placebos, but given the horror of the disease and the swiftness of the spread  whole villages were sometimes wiped out almost overnight in the weeks and months just past  the investigators drew up a different approach, called "ring vaccination," and subjected it to a panel on ethics because some subjects in the test might get effective protection, and others would not.

Researchers recruited 7,651 subjects who fit a rough profile of those who had been exposed to the Ebola virus, or to someone who had been exposed. These subjects were not then hard to find in spring and early summer. They were divided into two groups, with one group to get immediate vaccination and the other to wait 21 days. Once vaccinated, all were carefully tracked for several weeks. No one in the group that got an immediate vaccination developed Ebola in the first 10 days after vaccination. Sixteen subjects in the group whose vaccination was delayed developed the disease.

The most sobering treatment of the understandable near-giddiness is the caveat posed in Lancet: "More data on efficacy are needed before it can be widely deployed." The logical next step would be testing it against placebos in a much larger clinical trial. Ironically, this might not be possible until there is another epidemic, where a remote village struck by Ebola epidemic could be subjected a vaccine.

Bringing the Ebola epidemic of 2015 under control was a remarkable exercise of modern medicine in a sea of barely imaginable ignorance and superstition. Once out of the cities  where the limits of modern medicine are problematic enough  and into the remote back county, the suspicion, resistance and hostility to the little-known modern know few bounds. When the family and friends of one sickened doctor managed to arrange a flight out of Africa, several countries denied him permission to fly through their air space, terrified that the virus would drop from 30,000 feet.

The fight to control and suppress the Ebola virus is a remarkable story of how science and religion can be allies. Many of the doctors and nurses who risked their lives, some paying with their lives, were evangelical Christian missionaries living their faith. To science the credit, to G0D the glory.